In some scanning imaging systems such as scanning mammography systems, the object to be imaged is scanned by movement of the imaging system's detector. Some of these scanning imaging systems include an interferometer arrangement that allows grating based phase contrast imaging. See for instance C. Kottler et al, “Grating interferometer based scanning setup for hard x-ray phase contrast imaging”, Rev. Sci. Instrum. 78, 043710 (2007).
The proposition in phase contrast imaging is that radiation intensity as detected at the detector does not only encode information on absorption (traditional x-ray radiography is based on this) but also holds information on refraction experienced by the radiation in its passage through the object to be imaged. Phase contrast imaging then uses a number of techniques referred to as “phase retrieval” which is the task of extracting this refractive information from the detected signals.
It has been observed that, when a fixed interferometer setup is used, i.e., one where the gratings are fixed with respect to each other during image acquisition, calibration proves remarkably cumbersome. For instance, some approaches use specially designed phantom bodies.